Is it permissible to join a group about whom there is a suspicion that they are Sufis?

Question:
I was studying in America and I got to know the Da'wah group there, so I went out with them. By the grace of Allah, and then by their effort, many young people were guided, and praise be to Allah. When I returned to Saudi Arabia, some doubts about them came to me, that they are Sufis and so on. So what is your view, Your Eminence? Do you see any harm in continuing with them, or in leaving them, as if it were the same group?

Answer:
There is no harm in it. Walking with them, cooperating with them in the Da'wah, and if you see something we disapprove of, advise them. Because some of them may have some mistakes, some errors. I mean, some of them have this. So if the scholars gather them and guide them, and those who are slower among them, that would be safer for the Muslims.
Because Allah has made much benefit through this group. They traveled to many countries, until the situation became widespread. So Allah made much benefit through them for many people. So those who walk with them and participate with them, they should help them with others, encourage them with others, and support them. And if they find something, they should advise them and turn them back.